Paper chromatography circular

Their characteristic optical rotatory dispersion or circular-dichroism curves, and their infrared spectra, rich in characteristic frequencies, may be useful. Paper chromatography permits preliminary identification of the glycosyl phosphate or monosaccharide resulting after degradation, and the specific enzymic reactions of these products are widely used to provide additional evidence. 

A very efficient thin layer form of circular paper chromatography makes use of a circular glass disc coated with an adsorbent (silica, alumina or cellulose). The apparatus is called a Chromatotron (available from Harrison Research, USA). The disc is rotated by a motor, and the sample followed by the eluting solvent are allowed to drip onto a central position on the plate. As the plate rotates the solvent elutes the mixture, centrifugally, while separating the components in the form of circles radiating from the central point. When elution is complete the revolving circular plate is stopped and the circular bands are scraped off and extracted with a suitable solvent. 

There are several modifications of paper chromatography, including the "circular filter chromatography . For detailed description of various techniques, see Refs 31, 34, 42, 47,... 

The different methods of arranging the filter paper in the chromatographic chamber have been applied to sugar separations descending, ascending,39 40 and circular or horizontal development.41 These methods and other techniques will be discussed below. Detailed descriptions of the equipment needed for paper chromatography are readily available.8... 

Selenates and Selenites.—The separation of selenate and selenite ions by circular paper chromatography has been described.299 The significance of... 

Oreskes, I., and Saifer, A., Qualitative determination of amino acids in protein hydrolyzates by circular paper chromatography. Anal. Chem. 27, 854-856 (1955). 

Complementary to paper chromatography, but used more frequently because of the wide availabihty of stationary phases, is thin layer chromatography (TLC). It is simple, fast, reproducible and can achieve high resolution. It is usually performed on a square plate or on strips. A variation of this type of planar chromatography is carried out on a rotating circular plate using an instrument called a Chromatotron. 

For equivalent conditions the R values for circular paper chromatography are generally larger than those for paper strip chromatography. The R values for circular paper using... 

Perhaps the most attractive feature of filter paper chromatography is the ability to make fast, quantitative separations of simple or complex mixtures. The use of circular paper with central solvent feed Increases separation speed due to the two-dimensional flow of the solvent. In addition the solvent flow rate can be adjusted over moderate limits by charging the width and length of the tab or wick which delivers the solvent to the center of the paper (L15). By using circular paper Martin (M15) has separated lead from copper, arsenic, silver, cadmium, antimony, mercury and bismuth In... 

LI5 - R- J. LeStrange and R. H. Milller, "Circular Filter-Paper Chromatography", Anal. Chem. 26, 953 (1954). 

Auler [20] in his detailed survey on the analysis of antioxidants and accelerators was able to reproduce Zijp s work, and in addition, he applied the same solvent systems to circular paper chromatography with satisfactory results. 

The use of apparatus which has been developed for centrifugal paper chromatography (Firms 11, 58) can be extended to TLC also. Kokzun and Bbady [375] have thus separated in 10 min a mixture of dyes on circular glass or aluminium plates (20 cm diameter) at a speed of 500—700 revs/min. In the ordinary way, this separation requires 35 min. 

Detailed comparisons of TLC to other chromatographic methods, especially HPLC, and TLC to HPTLC are presented in Chapter 1 of Ref. 1. TLC involves the concurrent processing of multiple samples and standards on an open layer developed by a mobile phase. Development is performed, usually without pressure, in a variety of modes, including simple one-dimensional, multiple, circular, and multidimensional. The detection of zones is done statically with an assortment of diverse possibilities. Paper chromatography, which was invented by Consden, Gordon, and Martin in 1944, is fundamentally very similar to TLC, differing mainly in the nature of the stationary phase. Paper chromatography has lost favor compared to TLC because the latter is faster, more efficient, and allows more versatility in the choice of stationary and mobile phases. 

In addition to cellulose papers, modified-cellulose papers and glass-papers are also used for specific purposes. It is difficult to decide whether some self-supporting layers such as micropore membrane filter sheets or powders held in glass-paper sheets should be included among papers or thin layers. Paper chromatography is carried out in a descendant, ascendent or radial (circular) fashion. The diversity of the technique and the innumerable purposes to which it can be applied are discussed fully by textbooks and bibliographies, to which the reader is referred. 

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